302 IOWA STUDIES IN NATURAL HISTORY 
dropped into an opening in a lawn and entered an irregular tun- 
nel four to ten feet high. This is but one of many subterranean 
passage-ways which underlie sections of the city. They are the 
result of the forward movement of the liquid lava after a crust 
had formed by cooling on the surface of the flow. In places the 
floor showed ropy lava, and on it here and there our candles 
lighted up ‘‘whirls’’ of rudely circular ridges. In one place the 
floor crust had turned over while yet viscous, in another slow 
solidification had partly blocked the tunnel, and in still another 
the roof had fallen permitting a later flow to enter and join the 
viscous mass below. From the roof hung lava pendants which one 
learns to avoid after bumping into them once or twice. 
Rangitoto, mentioned above, is the largest and apparently the 
freshest of the Auckland voleanoes. A visit to the cone was made 
possible through the kindness of Mr. Hamer, chief engineer of the 
Harbor Board. A fast launch with Mr. Povey as guide quickly 
negotiated the nine miles of water. The cone rises out of the bay 
forming a nearly circular island eight to nine miles in diameter 
and 920 feet high. Approach to the shore is difficult since the 
jagged edges of the successive lava flows make an irregular saw- 
tooth coast-line which lacks sheltered bays. From a strongly 
built wharf a path leads up to the summit. The surface is a suc- 
cession of strong, clinkery, pressure ridges of broken, porous lava 
blocks standing at all angles and presenting an all but impassable 
terrane. In spite of heavy rainfall, vegetation has only a precar- 
ious foothold on the unweathered lava. In places large areas of 
the surface are quite barren, and the black lava, from a distance, 
resembles a freshly plowed field. On the more abrupt central 
part the scoria slope offers a more hospitable habitat, and vegeta- 
tion is more abundant but not dense. On the south slope are two 
small parasitic cones. Between them and the main cone is a de- 
pression, wooded and sheltered; these together with the 200 foot 
crater, are the main retreats of the nearly wild sheep and walla- 
bies introduced on the island some years ago. The summit yields 
a good birdseye view of Auckland, its harbor, and suburbs. At 
the east end of Rangitoto the Harbor Board has established a 
quarry and a stone crusher for obtaining stone for making moles 
and for crushed rock in cement work. Sand and gravel are negli- 
gible in amount about Auckland, and the ‘‘papa’’ rock, described 
above, is far too soft for construction purposes. For this reason 
